Transmission of pictures by electricity



H. E. IVES TRANSMISSION OF PICTURES BY ELECTRICITY Feb. 21, 1928.

Filed March 18. 1926 10 5 f r AME RkF. 1/ SEE E 6 lnue/zfan Patented Feb. 21, 1928.

UNETED STATES E ATENT OFFECE.

HERBERT E. IVES, OF MONTCLAIR. NEW JERSEY, ASSIGNOR TO \VESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TRANSMISSION OF PICTURES BY ELECTRICITY.

Application filed March 18,1926.

This invention relates to the transmission of pictures by electricity and more especially to a novel optical arrangement suitable for use in such systems.

The invention is in the nature of an im provement upon the system disclosed in the application of H. E. Ives, Serial No. 711,755, filed May 8, 1924. In that application there is disclosed an electromagnetic light valve of the single string type for controlling the exposure of elemental areas on a photosensitive receiving film. The size of the exposed elemental areas is determined by cer tain aperture forming elements which constitute integral parts of the light valve proper. These elements comprise a vibrating string, a fixed aperture inthe light valve pole-piece and an adjustable aperture or set of jaws for controlling the effectiveness of the received currents. .Because of the proximity of these elements and because of the delicacy of the vibrating string, the adjustment of such a valve, as regards the degree of exposure to be attained is sometimes difficult.

It is an object of this invention therefore to improve the efliciency of picture reproducing mechanisms by providing an optical system which is characterized by simplicity of organization and ease of adjustment.

Another object is a method for exposing a photosensitive receiving surface in equal successive areas to light uniformly distributed over each area and with an intensity determined by received picture currents.

A feature of the invention relates to a combination of light controlling apertures and lenses for determining the character and size of elementary exposed areas of a receiving film, as well as the particular portion of a received carrier wave to be etfec tive in the picture reproduction.

Other features and advantages of the invention will be apparent upon a consideration of the description given hereinafter and as pointed out in the appended claims.

It is to be understood that the terms used herein in reference to a picture both in the specification and claims do not limit this invention to the production of a picture record at the receiver from a picture record at the transmitter. The invention is equally applicable to systems, for example, in which a transitory image of a still or moving pic- Serial No. 95,578.

turc or object is produced at the receiver, as in certain forms of television systems.

The term light as used herein includes not only radiations within the visible spectrum, but also radiations having wave lengths above and below those of the visible spectrum.

Referring to the drawing Fig. 1 shows, schematically, apparatus and circuits at both the sending and receiving stations of a picture transmission system embodying the present invention.

Fig. 2 is a detailed showing of the relation between the light valve apertures and the vibrating string.

Fig. 3 is a detailed showing of the device for adjusting the size and character of the exposure on the receiving film.

Fig. 1 is a detail of other adjusting means for determining the bias or what particular portion of the curve of the received current will be effective in reproducing the picture.

The same reference characters are used in the several figures to indicate corresponding elements.

Referring to Fig. 1 an amplifier-modulator 1 is supplied with carrier currents from a source 2, and with picture currents from a photoelectric cell 3. The output of the amplifier-modulator 1 is impressed upon the line 11. after passing through a filter 4. The photoelectric cell 3 is located within the transparent drum 5 which is driven in any suitable manner from shaft 6. Mounted on drum 5 is the picture 7 in the form of a film. Light from source 8 is focused by means of lens 9 upon the picture film after passing through an aperturein the screen 10. The amount of light reaching cell 3 is determined by the transparency of the particular element which happens to be in alignment with the opening in screen 10 and the light from source 8. The amount of light incident upon the active element of cell 3 in turn determines the amplitude of current which is impressed upon the modulator 1. Thus, the currents from source 2 are modulated in accordance with the characteristics of the successive elements of the picture film which is scanned in a continuous helical path.

Referrin schematica to the receiving station shown y in the lower portion of Fig. 1,

the modulated carrier currents from line 11 after passing through filter 12- are amplified by device 13 and are impressed upon the string 16 of the light valve 17. The string lifi'issuspende'dwithin thevalve 17 so as to vi-hi-ate 'inthe direction of the trace on the receiving film 29. The optical system for the receiving stationshown sch'emati cally in horizontal section. I

Light from source 18 directedby means of lens 24 upon the string 16. The lampn18 i'spreferably of such a type as to intensely and uniformly illuminate the; opening;.19'. The. light valve l'Tcomprises a winding. 25 which is. mountedlon ahollow' central core Qf ithe 'magrietih frame26..QA plateYZYQ spond'to a completely transparent element of .the picture being, transmittedl, Tile-reproducing, fil nli29l ismounted upon drpm" 30 which is driven from sliat' 31. in: a: manner identical with. theidiifving of drum 5. For thepurpose o'fwhtrollihg; tli'e exposureof film 29,12, series of: adjustable; plates, in terposedbetween the light 'valveJfllandzthe film 29. other these plates, namelybafie Pl e 9;,is shown in' detaili This platehas ,ope'ning 2'3 in thejcent'ralfportion thereof which is adapted" to lie placed: aligmnent with the opening528 of thelight valve. and' the :opening ,lietween thelplate's :32 and; 331 Bafil plate 29 is hiveted'or'fa'stened in. any desired manner. to-the bracket" 34, Bracket 34? is suitably mountedupen: the main frame 35 and may he adjusted'in'a vertical -or horizontal'direetion by, meansof the adjusting 'screws 36 and 37. respectively; For: the purpose of'controlling the efi ect'i-ve horizontals width (if-opening, 23 there is provided a vane 2-2 which maybe adjusted horizontally-in the guide. before the opening 23 b'y meansof the adjustingscrew 38. On the side of the plate 20 opposite to vane 22;there is positionedanothervane 21 which may be adjusted: vertically in the guides 52 liy means of. adjusting screw 39, By means of screws 38: and 39' thereforethe effectivearea of the' opening in plate: 20 may be readily varied; Interp osed between the plate2fland' the' receivingfil ni' is a set of'pla'tes 32, 3321s shown in Fig. 4'. Plates 32'and' 33 are' arranged to be moved towards, and' away from each other by means of the adjusting'screws'l' and-'42, and are so mounted that the opening between them is parallelto and in al1gnment.withlight valve string 16. Between the light valve and the Baltic plate 20 is positioned a lens 43 which focuses an in'iage of string 16 upon the slit between plates 32 and 33.- Similarly, between the plates 32 and 33 and the receiving film 29 is interposed lens 44 which focuses an image of the adj ustable opening in plate 20 upon the receiving film 29."

Since lens 44 focuses upon the opening in plate-20,'- the" size of'the elemental exposure of film 29 is determined by the effective opening in plate-20- which may be controlled 'Fortlie transmission.' of 'pictu res,, the comil iunication between the sending and receivin'gstationsjmajijbe madehy means of'a car rierchannel .or a radio telephone" channel stead'offth'e transmission' line 1-1, which-is shown. 1f The sending drum 5 and receiving drum 304 arerotated in' synchrom'sm by any suitable Imeanssuch as that deseribe'd'in the application of B; Long, Serial n3; eslsz fiiea December 18,.1923.' These drums are not onl' rotated in synchronism hut-lare also ,move axially along. the respective shafts 6 and13L the drum .5 rotates, carrier current, from"so uree 2. is modiilated toi'tlie' varying tonevalues of suecessiveeleniental areas oflthe picture 7 and are sent over the transmitting. channel to the receiving station where the modulated waves areiim ressedupon the string 16 of light valve 1 5 vAssume that the normal position of string. 16 is such that an image of said string is focused by means of lens 43- In cover the aperture between plates 32 and 33. as shown more clearly in- Fig. 4. In this condition the receiving. film- 29 is unexposed. As string. 16 vibrates in response to the received waves, the image oflsaid stringcm'respondingly uncovers the aperture between plates 32 and 33 allowing a proportionate amount of light to reach the film 29. The

siz eof the exposed areas on film 29 may be adjusted by means of Screws 38 and 39. This exposed area will therefore bear a definite relation to.the sizeof the effective opening in'pl'ate2O and will be uniformly illuminated;.. v

As mentioned above, when stringlfi is at rest, plates 32 and 33' maybe adjusted so that-the image of stringlti just covers the opening; betweenthe plates, or the plates may he so adjusted that an appreciable moveadjusted that the distance between them is equal to the width of the projected image of string 16, exposure of film 29 begins just as soon as string 16 begins to move. If the aperture between plates 32 and 33 is less than the width of the projected image appreciable movement of the string must take place before exposure begins. From the foregoing description it will be seen there- -fore that the size and character of the elemental exposed areas of the receiving film as well as the effective portion of the reeeived carrier waves may be readily adjusted at points external to the valve proper.

What is claimed is:

1. In a system for the transmission of pietures, a receiving station, a drum at said station said drum carrying a photosensitive reproducing surface, means for transmitting to said station a carrier wave modulated according to characteristics of a picture or object, an image of which is t9 be produced,

a light valve, and means external to said valve comprising a plurality of lenses and adjustable apertures for controlling the exposure of said surface according to the received waves and for determining the portion of said waves effective in such exposure.

2. In a system for the transmission of pic tures by electricity, means for modulating carrier waves according to the characteristics of a picture or object, an image of which is to be produced, means for im ressing said waves on a light valve, said lig t valve having a string shutter element responsive to the impressed waves, a receiving drum carrying a photosensitive reproducing surface, lplates having an adjustable aperture thereetween, means controlled by said string for illuminating said aperture with light of an intensity corresponding to the picture or object characteristics, and means for determining the portion of the received waves eflec tive in the production of an image of said picture or object, said last mentioned means comprising a lens for projecting an image. of said string on said aperture.

3. In a system for the transmission of pictures by electricity, means for modulating a carrier wave according to tone values of successive elemental areas of a picture or object,

an image of which is to be produced, means for impressing said modulated waves upon a single string light valve, an element carrying a photosensltive reproducing surface, plates located between said valve and said surface and having an adjustable aperture therebetween, means for determining the portion of a received wave effective in the production of the image of the picture or object, said last mentioned means comprising an optical system for projecting an image of said string on said aperture, and means for adjusting the relation between said plates and said string image.

4. In a system for the transmission of pictures by electricity, carrier waves modulated in accordance with tone values of successive elements of a picture or object, an image of which is to be produced, a moving light sensitive record blank, a source of light for said blank, a light valve having a mov able string, means external to said valve for providing an adjustable aperture parallel with said string, means for producing an image of said string at said aperture, said image completely covering said aperture when said string is at rest, a light baflie between said plates and said valve and having adjustable opening means controlled by said string for uniformly illuminating said opening with light of an intensity determined by the received waves, and means comprising the image projected on said aperture for controlling the portion of the received waves effective in the production of the image of the picture or object.

5. In combination, a light valve having a single string, a light bafile having a slit therein, a source of light, another light bafile having an opening therein parallel with said string, an element with a photosensitive surface, means for producing an image of said string at said slit, said image completely screening said surface when said string is at rest, means effective according to the amplitude of movement of said string to illuminate the opening in the first mentioned bathe, and means for adjusting the width of said slit to determine the particular amplitude of movement of said string at which the exposure of said surface takes place.

6. In combination, a light valve, having a single string, a carrier wave modulated according to picture or object characteristics, means for applying said carrier wave to the light valve to cause a movement of the string proportionate to the amplitude of said wave, an element having a photosensitive surface,

means for exposing said surface as soon as saidlight'valvc aperture, means for focusingwsai-d'rays at apoint between saidscreen and said ph'otosensitive element to uniformly illuminate said opening-andmeans for- 0- cusing; an image ofsaid illuminated opening upon said element.

8.-Inan electrooptical image producing system a source of image producing currents,- a light valve having a shutter movable under the influence' ofcurrents from said-source, an element upon which an image is tolj'e produced;--a'sourceof light of con-' stantintensity, a= first lens producing an image of the light valve-shutter at a point between said shutter and said image element, a light screening device having an opening therein and located between said shutter and the image of the shutter produced by said first lens, and a second lens producing an image-of said opening on said image element, whereby an elemental area of said image element is uniformly exposed'to light from said light source of an intensity determinedby the movement of said shutter.

In witness whereof, I hereuntosubseribe my-name this 16th day of March A. 11,1926.-

HERBERT E. IVES. 

